1. Field of the Invention
This invention relates to a method of treating the molten slag from a copper converter to recover copper and other valuable materials effectively therefrom.
2. Description of the Prior Art
The slag from a copper converter usually contains as much as 3 to 5% by weight of copper. It cannot, therefore, be thrown away, but must be treated to recover the copper and other metals therefrom. Flotation is the most common method which is used for collecting copper and other metals from the slag. In this method the slag is solidified and pulverized and then concentrates having a high content of copper are separated by flotation and recycled into a smelting furnace. In another method the slag in its molten state is recycled into a reverberatory or electric smelting furnace. There is also known a method which employs a reducing agent to treat the slag. However, since an electric furnace is mainly used for carrying out this method, it is impossible to stir the molten slag sufficiently to recover satisfactorily recover the copper.
The flotation method has a number of drawbacks. It does not effectively utilize the heat of the slag. A large amount of electric power is required for the pulverization of the solidified slag and the separation of copper concentrates by flotation. It is only the matte particles suspended in the slag that can be recovered by this method. It is impossible to recover the majority of copper, lead, zinc, nickel and other valuable metals that are chemically dissolved in the slag, as they are lost to tailings.
The slag contains a large amount of Fe.sub.3 O.sub.4. Therefore, if the molten slag is recycled into a reverberatory or electric furnace, it is likely to raise the bottom of the furnace and decrease its effective volume.
The method employing a reducing agent requires a long reaction time and is inefficient, as it is impossible to stir the molten slag and the reducing agent effectively. It usually employs a sulfide to form a matte. Some dissolution of the matte constituents into the slag is unavoidable. The shape of the furnace which is used for carrying out this method presents some difficulty in the separation of the metals to be recovered.